1. Field of the Invention
The present invention relates to a positioning apparatus for obtaining migration path data of a mobile object, a positioning method therefor, and a storage medium.
2. Description of Related Art
There has been a positioning apparatus using a function of directly positioning its own present position by using a satellite positioning system, such as a GPS (global positioning system), in conjunction with a function of indirectly calculating its own present position by means of autonomous navigation using a motion sensor equipped with, for example, an acceleration sensor and an azimuth sensor.
This positioning apparatus measures a moving direction and a moving distance of a mobile object, such as a walker or a motorcar, by using the motion sensor.
Then, this positioning apparatus sets a measured position obtained by using the satellite positioning system as a reference point and sequentially integrates the information of moving directions and displacement quantities to the reference point, and thereby the positioning apparatus can obtain locus data of a path along which the mobile object has moved.
The accuracy of the measured positions in the positioning using the satellite positioning system changes according to the location of positioning satellites, the electric waves of which have been received by the positioning apparatus, and the ambient environment including a building and the like.
Consequently, the positioning apparatus has a problem such that there is a case where the measured position includes a large measurement error in some conditions at the time of positioning.
Accordingly, Japanese Patent Application Laid-Open Publication No. 2004-233186 discloses a positioning apparatus that compares a parameter value indicating the accuracy of a measured position measured by a satellite positioning with a predetermined threshold value and calculates the present position by using the information of a moving direction and a moving distance that are measured with a motion sensor when the accuracy of the measured position measured by the satellite positioning is lower than a level set in accordance with the threshold value.
However, the error of the measurement included in the information of moving directions and displacement quantities obtained by autonomous navigation becomes larger by being accumulated in the information of the moving directions and the displacement quantities at each measurement, as the autonomous navigation is being continued.
Consequently, the positioning apparatus has a problem of the impossibility of obtaining accurate position data and locus data owing to the influence of the accumulation of errors included in the information of the moving directions and the displacement quantities that are calculated by adopted autonomous navigation.